Alcoholism, a disease of changed behavior, is believed to involve alterations in gene expression. The knowledge gap to be filled is that of understanding how ethanol regulates gene expression to produce behaviors associated with alcoholism. It is our long-term goal to understand the transcriptional mechanisms that underlie ethanol-induced changes in gene expression that produce these behaviors. Functional tolerance, a metabolism-independent reduction in ethanol sensitivity due to prior exposure, is a change in behavior that can cause increased alcohol consumption and speed the path to addiction. Experiments in mammals, worms, and insects show that BK channels play an evolutionarily conserved role in ethanol responsivity. The highly conserved slowpoke (slo) gene encodes BK-type Ca2+-activated K+ channels, which integrate Ca2+ signals and electrical signals and are central to modulating neural activity. In Drosophila, ethanol sedation induces slo gene expression, and this expression has been shown to cause functional rapid tolerance to ethanol sedation. It has recently been shown that epigenetic modification to gene promoter regions underlies important aspects of long-term changes in behavior caused by experience and drugs. These modifications are believed to form an extended code that regulates gene expression. Induction of slo expression has been linked to epigenetic modifications of histones across the promoter region of the gene. The central hypothesis, formed from substantial preliminary data, is that ethanol sedation activates transcription factors and produces histone modifications that together result in increased slo expression to produce tolerance. It is the objective of this proposal to identify the transcription factors and epigenetic histone modifications that cause ethanol-induced slo expression. This objective will be achieved by pursuing the following specific aims: 1) determination of the time course of ethanol- induced histone modifications across the slo promoter region; 2) identification of transcription factors that modify histones and induce slo expression in response to ethanol sedation; and 3) identification of the cis-acting enhancers in the slo promoter region that are used in the ethanol-stimulated modification of histones and that are involved in the induction of slo. This work is innovative because it uses the unique toolset of Drosophila to study the epigenetic regulation of a gene known to underlie functional ethanol tolerance. The research is relevant to the mission of NIH/NIAAA because it has the potential to illuminate the fundamental mechanisms underlying functional tolerance and thereby the path to alcohol addiction.